China was struggling Thursday to restore several government websites that international hacking group Anonymous says it attacked in an apparent protest against Chinese Internet restrictions.

On a Twitter account established in late March, Anonymous China listed the websites it says it hacked over the last several days. They include government bureaus in several Chinese cities, including in Chengdu, a provincial capital in southwest China.

Some of the sites were still blocked Thursday, with error messages shown.

Anonymous activists have defaced websites around the world. They are engaged in political causes, including opposition to the global clampdown on file-sharing sites and defense of the secret-spilling site WikiLeaks.

Some websites that Anonymous said it attacked were working Thursday, and government officials denied the sites were ever hacked. China's National Computer Network Emergency Response Technical Team was not available for immediate comment.

In a message left on one of the hacked Chinese sites _ cdcbd.gov.cn, a home page for Chengdu's business district _ the hackers expressed anger with the Chinese government for restrictions placed on the Internet.

"Dear Chinese government, you are not infallible, today websites are hacked, tomorrow it will be your vile regime that will fall," the English-language message read. "What you are doing today to your Great People, tomorrow will be inflicted to you. With no mercy."

The message also offered instructions on how to circumvent China's restrictions on its Internet. The government tries to block Internet users in China from seeing social media sites such as Facebook and Twitter. Information on politically sensitive topics is often blocked.